Good description of the science AND art of software development

From Joel on Software, read the full article

Design is the art phase, where you’re doing new, creative work. Even though what you’re doing is completely new, after you’ve gone through a few software development cycles you’ll start to get a pretty good idea of how much time it takes to design a new version of your software. I’ve usually worked with relatively long development cycles of 12-18 months, and it’s always taken me about two months to get a detailed, first-draft spec containing enough detail for the development team to create very granular estimates.

That said, when you’re building something brand new from scratch, you really can’t estimate the design phase at all, and that’s OK. Today I met somebody from a company in Seattle that’s working on a project headed up by one of the world’s great programmers, Charles Simonyi. Near as I can tell, they have been in the design phase for 16 years.

Development is the engineering phase. It’s a construction project. As long as you start with a detailed blueprint, which, of course, can change over time, but which is really your best guess for what you’re building, this phase can be scheduled with great precision. FogBugz 6.0 has a spiffy new feature called Evidence-based scheduling, which uses a variation on the Monte Carlo method for making your schedules remarkably reliable during the development phase. When I get a chance, I’ll you about it in more detail.

Debugging is the science phase. Science is difficult to schedule because you’re looking for things, and predicting when you’re going to find them is remarkably difficult. Unless you know in advance how many bugs you’re going to find, you don’t have an ice cube’s chance in the Sahara to work out a detailed estimate of how long this phase will take. Here at Fog Creek we’ve learned that for a new release of FogBugz, this phase takes at least 12 weeks, sometimes a little more, and we just leave it at that.